H-plane reflex bend for a two layer pillbox antenna utilizing a plurality of holes to couple the layers



June 7, 1966 s LERNER 3,255,456

H-PLANE REFLEX BEND FOR A TWO LAYER PILLBOX ANTENNA UTILIZING A PLURALITY OF HOLES 'I'O COUPLE THE LAYERS Filed March 8, 1963 FIG. 2

FIG. 4 FIG. 5

United States Patent-O David S. Lerner, Flushing, N.Y., assignor to Hazeltine Research Inc., a corporation of Illinois Filed Mar. 8, 1963, Ser. No. 263,782 1 3 Claims. (Cl. 343780) This invention is directed to H-plane reflex bends and also to pillbox antennas utilizing such bends.

The objects of this invention are to provide new and improved H-plane reflex bends for waveguides and pillbox antennas utilizing such bends.

In accordance with the invention a two layer pillbox antenna incorporating an H-plane reflex bend comprises two waveguides formed by three aligned spaced parallel plates, the intermediate plate having a predetermined pattern of coupling holes piercing it near one extremity, and a reflector terminating both of the waveguides in the vicinity of the coupling holes and a feed coupled to one of the waveguides; whereby the combination of the reflector and the coupling holes causes a wave issuing from the feed and propagating toward the reflector to be coupled into the other waveguide and propagated away from the wall and ultimately into free space.

For a better understanding of the present invention together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the drawings, FIGS. 1, 2 and 3 are three views of an H-plane reflex bend constructed in accordance with the invention and FIGS. 4 and 5 are two views of a pillbox antenna utilizing the invention.

Referring now to FIGS. 1, 2 and 3, it will be seen that FIGS. 2 and 3 are sectional views of the FIG. 1 reflex bend. As shown, the reflex bend includes two waveguides formed by three aligned spaced parallel plates 10, 12 and 14. These plates may be constructed of metal. As shown in FIG. 3, the intermediate plate 12 has a predetermined pattern of coupling holes 16 piercing it near its left-hand extremity. As illustrated, the reflex bend further includes a reflecting wall 18, shown substantially perpendicular to the plates 10, 12 and 14,

tromagnetic wave having its electric field parallel to the plates, as indicated by the arrow 20 in FIG. 3, is propagated down one Waveguide toward the Wall 18. Half of the power of this wave will be coupled, via the holes 16, into the other waveguide. Then both the original and the coupled wave will be reflected from the wall 18 and on passing the holes 16 for the second time, the remaining power in the first waveguide will be coupled into the other waveguide. The wave will thus be coupled from one of the waveguides into the other waveguide. The wave will thus be coupled from one of the waveguides into the other waveguide.

The complete reflex bend just described with reference to FIGS. 1, 2 and 3 may be considered to be a directional coupler with complete coupling and with an image plane at the center. The design and operation of directional couplers are well known. The design and placement .of

Patented June 7,1966

the holes 16. can be determined by well known principles used in the directional coupler art, such as taught by N. Surdin, Directive Couple-rs In Waveguide, Journal of the Institute of Electrical Engineers, vol. 93, Part III-A, No. 1946, pages 725-736, and it is not necessary to discuss those design principles in detail here.

Referring now to FIGS. 4 and 5, there are shown two 'views of a two'layer pillbox antenna incorporating an H-plane reflex bend in accordance with the invention. As shown, the antenna comprises two waveguides formed by three aligned spaced parallel plates 32, 34 and 36, a parabolic reflector 38 terminating both of the waveguides and a feed 40 coupled to one of the waveguides. Referring to FIG. 4, if a section of the pillbox antenna as indicated by the dotted line and associated sectional arrows AA is removed and examined, it will resemble the arrangement shown in FIG. 1 and in the sectional views of FIGS. 2 and 3 (in a section such as AA the wall 18 would of course be slightly curved in FIG. 3). Thu-s the pillbox antenna of FIGS. 4 and 5 includes a reflex bend directly to the right of the parabolic reflector 38 in the FIG. 4 view. The holes such as 16 will appear in the intermediate plate 34 and will not be visible in the FIG. 4 view.

In operation, the 2-layer pillbox antenna of FIGS. 4 and 5 operates as follows. Waveguide 40 is coupled to the parallel plate waveguide defined by the plates 32 and 34. Waves coupled to the right-hand end of waveguide 40 in FIG. 4 will propagate in the parallel plate waveguide defined by the plates 32 and 34; one ray path is indicated by the dashed line 42. Upon the reaching the combination of coupling holes and the reflector 38, the wave will be coupled into the second of the parallel plate waveguides defined by plates 34 and 36. The wave will then be propagated in the waveguide defined by the plates 34 and 36 in a direction away from the reflector 38, the continuation of the original ray path being indicated by the dot-dash line 44. These waves will ultimately be coupled into free space as indicated by the arrow 46. The general design considerations involved in designing pillbox antennas are well known and need not be considered in detail here.

The pillbox antenna of FIGS. 4 and 5 also includes two additional aligned spaced plates 48 and 50, which are each connected perpendicularly to the plates 32, 34 and 36. The plates 48 and 50 effectively enclose the sides of the antenna. The invention isalso applicable to common rectangular waveguide. It can be considered that in such applications the plates 48 and 50 are moved close together so as to form rectangular waveguides of standard dimensions. Where the invention is used with such rectangular waveguide, it is considered preferable to use a flat reflecting wall such as 18 in FIG. 3.

While therehave been described what are at present considered to be the preferred embodiment of this in vention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is: 1. A two-layer pillbox antenna incorporating an H- plane reflex bend comprising:

two waveguides formed by three aligned spaced parallel plates, the intermediate plate having a predetermined pattern of coupling holes piercing it near one extremity; a reflector terminating both of said waveguides in the vicinity of said coupling holes; and a feed coupled to one of said waveguides;

whereby the combination of said reflector and said coupling'holes causes a wave issuing from said feed and propagating toward said reflector to be coupled into the other waveguide and propagated away from said wall and ultimately into free space.

2. A 2-layer pillbox antenna incorporating an H-plane reflex bend comprising:

two wave guides formed by three aligned spaced par allel plates, the intermediate plate having a predetermined pattern of circular coupling holes piercing it near one extremity;

a parabolic reflector, substantially perpendicular to said plates, terminating both of said waveguides in the vicinity of said coupling holes;

and a feed coupled to one of said waveguides;

whereby the combination of said reflector and said coupling holes causes a wave issuing from said feed and propagating toward said reflector to be coupled into the other waveguide and propagated away'fro said wall and ultimately into free space.

3. A 2-layer pillbox antenna incorporating an H- plane reflex bend comprising:

two similar waveguides formed by three aligned spaced parallel metallic plates, the intermediate plate having a predetermined pattern of coupling holes piercing it near one extremity; a

a parabolic reflector terminating both of said waveguides in the vicinity of said coupling holes; and a 'feed' coupled to one of said waveguides:

whereby, when an electromagnetic wave having its electric field parallel to the plates is propagated down one waveguide from said feed toward said reflector, half of the power of said wave is coupled via said holes into the other waveguide, both the original and the coupled waves are then reflected by the reflector, and on passing said holes the second time the remaining power in said one waveguide is coupled into said other waveguide.

References Cited by the Examiner UNITED STATES PATENTS HERMAN KARL SAALBACH, Primary Examiner.- W. TAYLOR, P. L/GENSLER, Assistant Examiners. 

1. A TWO-LAYER PILLBOX ANTENNA INCORPORATING AN HPLANE REFLEX BEND COMPRISING: TWO WAVEGUIDES FORMED BY THREE ALIGNED SPACED PARALLEL PLATES, THE INTERMEDIATE PLATE HAVING A PREDETERMINED PATTERN OF COUPLING HOLES PIERCING IT NEAR ONE EXTREMITY; A REFLECTOR TERMINATING BOTH OF SAID WAVEGUIDES IN THE VICINITY OF SAID COUPLING HOLES; AND A FEED COUPLED TO ONE OF SAID WAVEGUIDES; WHEREBY THE COMBINATION OF SAID REFLECTOR AND SAID COUPLING HOLES CAUSES A WAVE ISSUING FROM SAID FEED AND PROPAGATING TOWARD SAID REFLECTOR TO BE COUPLED INTO THE OTHER WAVEGUIDE AND PROPAGATED AWAY FROM SAID WALL AND ULTIMATELY INTO FREE SPACE. 